A nitride semiconductor device has characteristics such as a high saturation electron velocity, a wide band gap and so forth. Development of a high voltage withstanding and high output device is being performed lively utilizing the characteristics.
As a nitride semiconductor device that is used in such a high voltage withstanding and high output device as just described, a field effect transistor, especially, a high electron mobility transistor (HEMT), is available.
For example, an HEMT (AlGaN-HEMT) in which an AlGaN barrier layer is stacked on a GaN channel layer is available. Further, also research for an HEMT (InAlN-HEMT) in which an InAlN barrier layer is stacked on a GaN channel layer is being performed.